lauck@bergil.DEC (05/10/85)
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Recently, I borrowed a Nakamichi OMS-7 CD player from a nearby dealer and
compared it to my Sony CDP-101 which I've had for 18 months. I told the
dealer that I wasn't in the market for a new player, just curious to see if
CD players had improved significantly. He confidently approved the loan.
In non-blind listening tests, my wife and I much preferred the Nak to the
Sony. Many of my CDs were unlistenable on the Sony, due to excessive glare.
The new player removed the glare from these recordings, making them listenable.
It improved the imaging of nearly all of our CDs. The soundstage
was much wider and the images more specific. Depth was
substantally improved on most recordings. On a number
of multi-miked recordings it became possible to hear the
individual sound fields of separate microphones.
Based on this promising development, I repeated my CD vs. LP comparisons of
last year, with a three way comparison of LP, Sony CD and Nak CD.
Two recordings were used, the Sheffield "West of Oz" direct disk LP and
digitally mastered CD, and the Reference Recording "Tafelmusik" which
was analog mastered (using Prof. Johnson's special recorder).
On "West of Oz" about half of the subjective difference between the
CD and LP was eliminated when switching from Sony to Nak. The remaining
differences were not significant on much of the program material.
The differences were of the same order of magnitude as those introduced by
moving coil step-up transformers. (The LP was preferred on all cuts.)
On "Tafelmusik" the new player subjectively eliminated 75% of the difference
between CD and LP. On many cuts there were extended portions with no
significant difference between LP and CD. Occasionally, the LP did a better
job of separating the instruments and keeping the images from
moving. Sometimes there was a partial soundstage "collapse"
with the CD. The differences were slight. I would not want to bet too much
money on passing a double-blind test between CD and LP. The next time I
decide to listen to "TafelmusiK" for its musical value I will probably play
the CD due to convenience and cost factors. (Lasers are cheaper than
diamonds.)
I returned the unit to the dealer, telling him I liked it but couldn't
afford it. He was able to arrange a nearly even trade for an old Mac 275
amplifier and an inoperative old Marantz 10B tuner. I am now a happy
OMS-7 owner and have begun purchasing CD's again.
Other equipment used in the comparison was:
Record player: Thorens TD125, SME series II, Monster Alpha-1
Preamp: Marantz 7 (solid state), phono straight-in with 50 ohms load
Amp: VSP Labs Gold Edition
Speakers: Snell Model A, series II.
(The speakers are on a separate floor, precluding feedback.)
For the curious, the Sony has a single 16 bit DAC and analog filtering. The
OMS-7 uses two 16 bit DACs, and has 4X oversampling.
Lest I start any flaming, I make no claims that these results will be
repeatable by different people, in a different room, or with different
equipment. They only represent my personal opinion. I advise any
prospective buyer of audio equipment to listen carefully in his or her own
home before buying. This requires doing business with a good dealer.
Shortly after buying the OMS-7 I took it over to a friend who is a digital
recordist, author for above-ground hi-fi magazines and an avocate of
double-blind testing. On his system we heard no difference between the
OMS-7 and either a Sony CDP-101 or a variable speed Technik's player.
(The latter is recommended for double blind tests, as it facilitates
synchronization.) A different test technique was used. Instead of
playing several minutes of music and repeating the same selection, we
switched rapidly between players. With this technique we could hear
no subjective differences. Not surprisingly, our blind tests were not
statistically significant.
When I get some more time, I intend to find out why the double-blind
tests were unsuccessful. They did not change my opinion of the OMS-7.
Tony Lauck
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